Manual Pages  — PFIL

Packet filtering points, for historical reasons named heads, are registered with pfil_head_register(). The function is supplied with special versioned struct pfil_head_args structure that specifies type and features of the head as well as human readable name. If the filtering point to be ever destroyed, the subsystem that created it must unregister it with call to pfil_head_unregister().

Packet filtering systems may register arbitrary number of filters, for historical reasons named hooks. To register a new hook pfil_add_hook() with special versioned struct pfil_hook_args structure is called. The structure specifies type and features of the hook, pointer to the actual filtering function and user readable name of the filtering module and ruleset name. Later hooks can be removed with pfil_remove_hook() functions.